But it was worth it to wait for somebody with their windows open about to take a drink of coffee..........
I have followed drivers down the road for miles, (too) close to their bumpers blaring everything I had to get them to move.
you don't need arduino, google for, 567 Tone Decoder (narrow bandpass filter) , electret microphone and frequency of siren.
(narrow bandpass filter) = Notch Filter
almost, opposite way